1. Field of the Invention
This invention relates generally to apparatus for correcting time base fluctuations in digital signals and, more particularly, to a time base error corrector using uncomplicated memory units.
2. Description of the Background
The reproduced analog video signals from a conventional video tape recorder (VTR) usually contain time base fluctuations that must be removed by time base compensation using the so-called time base error correcting apparatus (TBC). An example of one such system is shown in U.S. Pat. No. 4,054,903.
Such time base correction using a TBC is similarly employed in digital VTR's operating on digital video signals. The above-described conventional time base correction apparatus requires complicated circuitry in order to perform readout/writing control of the main memory that is employed In addition, the typical TBC apparatus is expensive due to the requirement for high-speed operation of the main memory. The circuitry is also cumbersome because it is necessary to provide a write address generator, a readout address generator, serial/parallel converters, and/or a parallel/serial converter.
In digital VTRs the usual practice is to perform the recording operation using multiple channels, because of the increased data volume and, typically, the data is recorded in eight channels. Consequently, the number of circuit elements in the above-described TBC is multiplied by the number of channels, resulting in quite a large-scale apparatus.
Another time base correcting apparatus in Japanese Patent Publication 63-72287 has been proposed, and this apparatus is designed so that time base fluctuations contained in the time base compressed signals are corrected by first-in first-out (FIFO) memories. In that system, although correction of the clock phase can be achieved, there is no provision made for correcting errors in the block phase of the digital signal.